#include "stdio_impl.h"
#include "pthread_impl.h"

int __lockfile(FILE *f)
{
    int owner = f->lock, tid = __pthread_self()->tid;
    if ((owner & ~MAYBE_WAITERS) == tid)
        return 0;
    owner = a_cas(&f->lock, 0, tid);
    if (!owner) return 1;
    while ((owner = a_cas(&f->lock, 0, tid|MAYBE_WAITERS))) {
        if ((owner & MAYBE_WAITERS) ||
            a_cas(&f->lock, owner, owner|MAYBE_WAITERS)==owner)
            __futexwait(&f->lock, owner|MAYBE_WAITERS, 1);
    }
    return 1;
}

void __unlockfile(FILE *f)
{
    if (a_swap(&f->lock, 0) & MAYBE_WAITERS)
        __wake(&f->lock, 1, 1);
}
